Transformer with a closed magnetic circuit



Oct. 3, 1939. P. sou;Y ARY TRANSFORIER WITH A CLOSED MAGNETIC CIRCUITFiled 001;. 1955 2 Sheets-Sheet l MOVHLE CU/L STAND/WWP CO/L MOVIQHLEPP/MMV COIL Attorney Oct. 3, 1939. P. soULARY 2,175,039

TRNSFORIER WITH A CLOSED MAGNETIC CIRCUIT Filed Oct. l5, 1936 2Sheets-Sheet 2 im 31k 56, MOI/AggL/ PRIN/)ky Inventor Attorney PatentedOct. 3, `1939 UNITED STATES PATENT OFFICE TRANS-FORMER WITH A CLOSEDMAGNETIC CIRCUIT France Application October 15, 1936, Serial No. 105,769In Germany October Z5, 1935 3 Claims.

The present invention relates to transformers with a closed magneticcircuit and a controllable magnetic leakage obtained by steplessdisplacing of one of the windings with respect to a stationary Winding.These transformers are used in the cases in which a reactive voltagedrop is to be obtained, for instance in electric arc Welding or inresistance welding.

In electric arc Welding it is necessary that it o should be possible tomake the intensity of the welding current to assume all values betweenthe limit values which it is desired to have available according tothenature of the metal and the bulk of the Work to be Welded, the diameterof the il Welding rods and the nature of their coating, etc. In the sameway in resistance Welding the trans.. formers of this kind can beadvantageously used as they permit the control of the welding current,particularly according to the thickness to the i nature of the metal ofthe work.

In the transformers of this kind heretofore manufactured, the windingsof the primary and secondary circuits are wound around a closed magneticcircuit, of rectangular or annular shape s and their relativefpositionis changed by displacing one of the windings with respect to the other,which is stationary. The rectangular construction requires a relativelylarge space in order to obtain all the desirable current ranges and Dthe annular construction in practice has the same drawback. Further thelatter presents certain diiliculties in manufacture or requires theentirely curvilinear cutting of the sheets of the core, which increasesthe costI of manufacture and in-- 'i volves sheet wastes which arepractically useless.

The transformers designed according to the present invention avoid allthese drawbacks and in particular occupy a small space and are easy tomanufacture. The transformer is characterized in that its closedmagnetic circuit is constituted on one hand by an incurvated part, along`which the movable winding can be displaced, and, on the other hand, byone or more rectilinear parts, which bridgesor bridge-the ends of thisincurvi ated part.

Preferably the incurvated part ofthe magnetic circuit is so shaped thatit renders possible the displacement of the movable winding along an arcof a circle and for example along a half-circle i and the rectilinearparts are constituted by two parallel cores and by a yoke perpendicularto these cores. Y l

In order to obtain a predetermined range of controlled currents with theminimum expendin 5 ture of raw material it is advantageous to reduce(Cl. T11-119) the magnetic circuit.

The invention is illustrated by way of examples in in the accompanyingdrawings in which:

Figure l is a transformer intended for use in electric arc welding,

Figure 2 is a modied form with an incurvated core of progressivelyvarying section,

Figure 3 is a transformer in which one of the circuits includes astationary winding and a movable winding, connected in series,

Figure 4 shows a device which allows the movable winding to assumeelastic displacements, and 2o Figure 5 shows a transformer for electricarc welding and resistance welding.

In the Figure 1 the magnetic circuit consists of a semi-circular part 'land of two cores 4 and 8; a yoke 9 closes this magnetic circuit. TheWind- 5 ing which is stationary with respect to the magnetic circuit isshown at l and surrounds the core 4. It forms the secondary Winding ofthe transformer and is connected to the electrode 4 and to the workpiece3. so

The second winding 5, which is therefore the primary winding, isconnected to a network; it can rotate about an axis 6 and surrounds thesemi-circular part 1 of the magnetic circuit. This axis can coincide, asin the case of the figure, with the centre of the semi-circular part ofthe magnetic circuit, or not. The winding 5 is so manufactured anddisposed that, during its rotation, it can be displaced from a positionof maximum coupling with the winding I to a position of minimumcoupling. In Figure 1, the movable winding 5 is represented in fulllines n its position of maximum coupling and in dotted lines initsposition of minimum coupling. These two limit values of the couplingcorrespond to an angular displacement of of the movable winding.

Owing to this arrangement of the magnetic circuit a very, tight maximumcoupling and a very loose minimum coupling are obtained and the spacerequired is reduced. o

The transverse sections of the magnetic circuit s can be square orrectangular or present any shape ascertained as advantageous from thepoint of view of the utilization of the raw materials or oi the ease ofmanufacture. The area of these u sections he cons" vary in continuousdis l e.. particularly if it is o advantage to cre sones ci" a more orless high saturation. along the may netic circuit, in order to obtainmodes ci distribution ci the values of the secondary cu:-

in relation with the angular displacemogt of movable wind igure 2 themagnetic circuit coy parallelopipedic yoke l@ and two cores l thetransverse sectionsY of which are un tl e core having the grea'ersection. c. curva-ted piece bridges the ends of ese cores and itstransverse section is progressively im duced 'troni the transversesection oi? the core li transverse action or the core i3, rrhe sec-1tion of ie il is crosseshaoed, vantageous connection v surface to hewound. The stationary ing situated at lll', around movable winding isshown at displacement of the movable winding in tion oi the arrow, thefree space between and the movable winding pr gressiv creases,which'oers the advantage, as against a magnetic circuit with a constantsection, that the current value changes less rapidly in the regions oitight coupling and therefore in the range of the higher currentintensities, and changes more rapidly in the range o the lower currentintensities.

in the Figure 3, relating to a transiormer in which one of the circuitsincludes a winding a movable winding, connected series, the magneticcircuit is constituted by semi-circular yoke i6, two cores and and arectilinear yoke lil. rThe primary is formed by two coils connected inseries: the one No is sta ticnary and wound around the core il; theother 2l is movable and can rotate about the which, in this illustratedconstruction, coincides with the axis of the semi-circular part of themagnetic circuit. The secondary coil is shown at It is to be noted thatthe highest leakage e'ect, which is obtained when thetwo primarywindings ill and 2l are in the nearest relative position, principallydepends on the total nurnber oi the primary turns, whereas the lowestleali'.- age effect, which is obtained when the winding 2l is in itsnearest position in relation to the stationary secondary winding,principally depends on the respective numbers of turns oi the windings2li and 2l. t is therefore possible, by properly choosing these numbersof turns, to obtain the maximum and minimum desired values ci thesecondary current and to simultaneously maintain an angular movement oiitil" o the movable winding, if this is deemed useful.

lllhis disposition Jfurther affords the advantage or" reducing thedimensions and the weight of the movable part and involves a betterutilisation o the free space in the opening of the magnetic circuit.

The transformers according to the invention can be provided withwindings having a number of taps to allow the obtaining of severalranges of control or several values oi no load voltage. lt is alsopossible to associate these transformers with other appliances such asreactance coils, capacities, resistances, or choke coils or threephase-single phase systems, current rectiiiers, etc. One can also usesimultaneously several of these transformers to constitute polyphasesystems, for example the three phase- ,Wo phase system for electric arcWelding,

the core l i, vthe Through the e direc is advantageous ior certain tions`oil these leakage tran rmers, to use a support o' the movable windingso constructed that under the inuence oi the electromagnetic repulsion,the movable winding assumes an elastic displacement in relation to itsequilibrium position of no load. conditions, which permits the usc,during a very brief space oi' time when the output circuit is put underload, oi current higher than the current necessary when under load. Forthis purpose, the mecha nical device that connects the winding to the diving axle can either be flexible in the direction of the angulardisplacements and assume elastic-deformations of position, or can be provided with a system articulations and springs, the latter being adj1table if necessary. When the utilisation circuit is under load, thecurrent intensity attains a predetermined value which corresponds to theequilibrium position ci no load conditions, then it progressivelydecreases until the winding assumes new equilibrium position., under thesimultaneous influences of its ertia, of the electromagnetic repulsion,ci the elastic tension exerted on the support and evenu tually ofgravity.

Figure e shows diagrammatically a device which allows the movablewinding to assume elastic displacements in relation to its equilibriumposition oi no load conditions. The support oi the winding movable alongthe magnetic ciru cuit is provided with a piece Eil, that rotates aboutthe axle under the action o the driving means of this support, and witha piece 2 to w ich is fastened the movable winding and which. isarticulated at on the piece lill. This piece "IC can rotate between twostops tu and Cil. i pri*- g Si? biases the piece 2d against the stop35i; he tension oi this springis adjustable by dislacing in a slot 33 ofthe piece 26 the block. to which is attached an end o this spring.weight lil is fixed to the piece for increasing the inertia o the 'wholedevice which rotates about the axle 2d. when the utilisation circuit isput under load, the electromagnetic repulsion exerted on the coil dfihas the eirect oi causing it to rotate about this articulation in thedirection indicated by the arrow. rlhe internal dimensions of thewinding maires this displacement possible.

Transformers in which current circuits are provided for several purposeswhich involve different electric characteristics can also be constructedaccording to the invention. One and same transformer can for instance beconstructed for clectric arc welding and for resistance Welding. Onecan, in this case, use windings with several taps, the sections ofwhich, in their different parts, correspond to the required currentintensities. One can also use several primary and secondary Windings,the movable parts of these windings being then preferably attached tothe same support.

lin the Figure 5, relating to a transformer for electric arc Welding andresistance welding purposes, the apparatus is provided with a .singleprimary winding constituted by the stationary coil 35 and the movablecoil 36, which are connected in series. rThe secondary Winding used forelectric arc welding is illustrated in 31: it is wound on the coreopposite the core on which the stationary primary winding is wound. Asecond secondary winding 38, independent of the 'lirst one, is woundconcentrically with the winding 35. The number of its turns and theirsection cor respond to the voltages and current intensities involved inresistance welding.

1t is to be noted that this transformer functions for electric arcwelding in an identical manner to the transformer illustrated in Figure3. The minimum coupling corresponds to the position in which the twocoils of the primary winding are nearest one to the other. On the otherhand, in resistance welding, the maximum coupling and therefore thehighest current intensity is obtained in the position where the twoprimary coils are nearest one to the other.

What I claim is:

1. In a closed magnetic circuit transformer, an incurvated core, twostraight core legs in alignment with the end parts of' the incurvatedcore, a yoke bridging the ends of said core legs, a primary windingmovable along said incurvated part, a first stationary windingmountedvaround one of the straight core legs and providing the secondaryof an external utilisation circuit and a second stationary windingelectrically independent from the rst stationarywinding, mounted aroundthe second of the straight core legs and providing the secondary of asecond external utilisation circuit.

2. A transformer of the character described, comprising aclosed-magnetlc-circuit core having a semi-circular portion, straightcore extensions projecting contiguous with the opposite ends of saidsemi-circular portion, a yoke bridging the free ends of said coreextensions, a stationary coil mounted upon one of said core extensionsand a movable coill displaceable arcuately on said semicircular portionabout an axis corresponding substantially to the radial center of saidsemiable coil being disposed around said semi-circular core portion andmovable through a full 180 arc, whereby said movable coil can be closelycoupled to either of said stationary coils.

PIERRE SOULARY.

